During the reporting period work on "Tinkerbell" was completed. Tinkerbell is an interactive volume editing program, written by Y. Li and J. Frank with some assistance from A. Leith. The user views source and destination volumes. The two volumes are displayed using volume rendering in real time. To obtain real-time performance the volume rendering is performed using the texture memory of a high-end graphics workstation. The user sees a three-dimensional cursor floating in the two renderings. Assisted by this cursor, the user can transfer material between the two volumes, selectively deleting or moving material from volume to volume. This editing occurs in real time and the views of the two volumes are updated as the editing occurs. Tinkerbell is useful for analyzing and displaying the results of tomographic and confocal microscopy reconstructions. It is especially useful for segmentation of complicated reconstructions which can not be segmented by algorithmic means. A paper on "Tinkerbell" was presented by J. Frank at the Schloss Ringberg conference on electron tomography in Munich, Germany. Y. Li went to the SGI European research lab in Basel, Switzerland on thier invitation, as a result of the Ringberg paper. Li, Y., A. Leith and J. Frank. 1997 Tinkerbell-A tool for interactive segmentation of 3D data. J. Struct. Biol., (In press)